Configured and sized cannula

ABSTRACT

A dilator retractor and the dilators that are used for minimally invasive spinal surgery or other surgery are configured to accommodate the anatomical structure of the patient as by configuring the cross sectional area in an elliptical shape, or by forming a funnel configuration with the wider end at the proximate end. In some embodiments the distal end is contoured to also accommodate the anatomical structure of the patient so that a cylindrically shaped, funnel shaped, ovoid shaped dilator retractor can be sloped or tunneled to accommodate the bone structure of the patient or provide access for implants. The dilator retractor is made with different lengths to accommodate the depth of the cavity formed by the dilators.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/523,033 (now U.S. Pat. No. 8,361,151) filed on Jun. 14, 2012 andentitled “Configured and Sized Cannula,” which is a continuation of U.S.application Ser. No. 12/776,857 (now U.S. Pat. No. 8,235,999) filed onMay 10, 2010 and entitled “Configured and Sized Cannula,” which is acontinuation of U.S. patent application Ser. No. 11/030,218 (now U.S.Pat. No. 8,192,437) filed on Jan. 6, 2005 and entitled “Configured AndSized Cannula,” which is a divisional of U.S. patent application Ser.No. 10/021,809 (now U.S. Pat. No. 7,008,431) filed on Oct. 30, 2001 andentitled “Configured And Sized Cannula,” each of which is expresslyincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to medical instruments for use in surgicalprocedures and more particularly to a wide-channel cannula that ispre-sized, pre-configured and tailored to conform to the patient'sanatomy.

BACKGROUND OF THE INVENTION

In one aspect of this invention, the invention considers the anatomicalshape of the area of the patient being operated on and tailors the shapeof the dilators and the dilator retractor or cannula to accommodate thatshape. In another aspect of this invention, the invention constitutes animprovement over the apparatus and method disclosed and claimed in U.S.Pat. No. 6,159,179 granted on Dec. 12, 2000 to the inventor of thispatent application and entitled “Cannula and Sizing and InsertionMethod” by providing different sizes of the same configuration ofdilator retractors.

As is well known by those skilled in this technology, the cannulautilized in the field of minimally invasive surgery is particularlyefficacious in performing such spinal medical procedures as laminotomy,medial facetectomy, foraminotomy, nerve root retraction, discectomy andthe like, is cylindrically shaped. I have found that a cylindricallyshaped cannula is not always ideal for certain surgical procedures andthis invention is intended to obviate the problems incidental to acylindrically shaped cannula and to increase the number of surgicalprocedures that can be performed by dilation methods by changing theconfiguration of the retractor tube or cannula. As is apparent to oneskilled in this technology, the anatomy of the human spine is not madeup of flat surfaces and a purely cylindrical device passed overcylindrical dilators and directed toward the lamina more likely than notsettles off of or partly on the bone. When this occurs, a tuft of musclemigrates to or is left between the bone and the bottom of the retractorand must be removed surgically. Obviously, this surgery is a source ofpain and discomfort for the patient and creates an additional surgicalstep for the surgeon. Moreover, this additional surgery causesadditional bleeding and as a consequence, creates an obstruction to thevision of the surgeon. In order to cure the obstruction, the surgeonmust address this problem through an electro cautery procedure.

Also apparent to one skilled in this technology is that the pathologicaltarget within the patient is often not an equal distance vertically andhorizontally. Hence, a surgical procedure may require a surgicalapproach that for ideal conditions, provides access that is morevertical in orientation than lateral. Obviously, a cylindrical device ashas been heretofore available and as disclosed in U.S. Pat. No.6,159,179 supra, which is equidistant from the axis, does not allow forthis approach. Thus, in a cylindrical cannula, in order to gainadditional vertical access the size of the cannula must be increased thesame amount in the lateral direction that it is in the verticaldirection. Obviously, the human spine's skeletal structure, i.e. lateralfacets and medial spinous process, restricts the amount of lateral spaceavailable. In a cylindrical cannula, since a limitation of the lateralspace that is available to locate a retractor, the vertical space islikewise limited. As a consequence, the cylindrical cannula limits thenumber of patients who are candidates for minimally invasive spinalsurgery necessitating the more invasive type surgery with all of theproblems associated therewith. Hence, for a large segment of the patientpopulation, the only surgery available is the more destructive invasivemuscle burning and stripping approach. This invention addresses thisproblem and provides a solution whereby the minimal invasive surgery isnow possible which otherwise was considered impossible to perform,unpractical or unpredictable in terms of surgical success or long-termoutcome.

The other aspect of this invention is the improvement to the systemclaimed in U.S. Pat. No. 6,159,179, supra. In this patent, the depth ofthe cavity at the location where the invasive procedure is beingperformed is measured and the surgeon can then select from a kit orinventory of different sized cannulas or retractors the desired sizerequired to perform the surgical procedure.

I have found that a solution to the problem noted in the immediate aboveparagraphs is that I provide in one embodiment of this invention,dilators and retractors that are configured other than in a cylindricalshape, such as an ovoid, and that I provide different sizes to meet theanatomical needs of a particular patient. By providing dilators anddilator retractors made in accordance with this invention, theseinstruments will be able to reach down between the facet joint and thespinous process to gently part muscle tissue and come into closercontact to the bony target. This will reduce or eliminate the need forthe surgeon to surgically remove otherwise valuable viable muscletissue. This will also reduce post-operative pain and inter-operativetime (fiddle). In addition to the above, this new design will allowsurgeons to address new pathologies in patients that previously wouldnot have been able to undergo a minimally invasive technique. To morefully appreciate the importance of this invention a common example isdiscussed immediately hereinbelow.

This example considers a patient with multilevel central canal stenosis.To address this patient's pathology, the surgeon may need over 35millimeters (mm) of vertical access. The typical lateral distance, i.e.,space between the spinous process and the facet joint, available at theL4 lamina is 16 mm. A 16 mm cylindrical retractor would fit tightlyagainst the lamina but even with “wanding” (moving up and down) it wouldrestrict the surgeons ability to reach much more than the 16 mm invertical access. The only option that is available to the surgeon,heretofore, is to utilize a cylindrical retractor. As explained above,since the equation for a cylindrical retractor mandates that the lateraland vertical expansions are equal, the cylindrical retractor wouldquickly reach beyond the practical or acceptable size for many, if notmost, multilevel patient candidates.

Another embodiment of this invention is the contouring or configuring ofthe bottom of the retractor in order to meet the requirements of certainoperation procedures and/or permit the retractor to be positioned closerto the target. This invention contemplates angling the tip in both acylindrical and ovoid shaped retractor and/or locating a tunnel in thebottom thereof which allows for a rod or implant to be passed throughthe distal tip of the cannula and into a pedicle screw (e.g., as shownin FIG. 5A).

While much has been accomplished in the medical field to limit tissuedisruption, use minimal incisions, reduce the hospital stay and increasethe speed in which the patient recovers, this invention is intended toraise the surgical procedure to a higher level. This invention in thefield of minimally invasive surgery is particularly efficacious inperforming such spinal medical procedures as laminotomy, medialfacetectomy, foraminotomy, nerve root retraction, discectomy and thelike.

As discussed in U.S. Pat. No. 6,159,179, supra, a typical procedure inperforming a lumbar discectomy is to advance a guidewire through a smallincision which is advanced to the inferior edge of the superior lamina.A small incision is then made that extends either cranially or caudally.A dilator is then inserted over the guidewire. Larger diameter dilatorsare sequentially inserted over each other to increase the opening intothe body cavity. Typically the guide wire is removed after the firstdilator is installed and eventually the dilators are all removed afterthe tubular retractor has been inserted over the largest of thedilators. Once these procedures are accomplished, the retractor islocked into position by a retractor clamp that is clamped to a retractorclamping arm which is fixed to a rigid member such as the operatingtable. This provides an unencumbered zone where the surgeon can performthe medical procedure that was intended to be performed. According tothe present invention, the dilators, of course will now conform to theconfiguration discussed above.

Instead of sizing the cannula to the largest depth that is anticipatedin the surgical procedure, the U.S. Pat. No. 6,159,179, supra, teachesproviding to the surgeon a series of different sizes in a kit so thatthe surgeon can measure the depth of the cavity of the patient andselect the requisite size from the kit. Hence, the surgeon measures thedepth by measuring from the exterior of the cavity to the most interiorposition in the cavity (inferior edge of the superior lamina) and thenselects, for example, either a 10 millimeters (mm), 20 mm, 30 mm, etc.as the situation requires. The dilator retractor will also have the samecross sectional shape as the dilator, but it may have a predeterminedconfiguration at the distal end. This invention improves the state ofthe art of spinal surgery by expanding the current boundaries ofminimally invasive surgery. This provides a new option to patients thatwould otherwise be delegated to the more disruptive open musclestripping surgical approaches. The ovoid design with or without theangled distal tip, allows a surgeon greater vertical access withouthaving to be encumbered by unnecessary lateral access.

Also, it is contemplated within the scope of this invention, that thedilator retractor will be provided in a kit where a given configurationwill be provided in a series of dilator retractors that have differentlengths, so that the depth of the cavity of the patient will determinethe particular sized dilator retractor that will be utilized for thatprocedure.

SUMMARY OF THE INVENTION

An object of this invention is to provide a cannula used in minimallyinvasive technique that is tailored for a patient and pathology.

A feature of this invention is to provide an ovoid shaped retractor anda complementary shaped dilators. Other configurations that are notcylindrical are contemplated within the scope of this invention.

Another feature of this invention is to contour the tip of the distalend of the retractor to match the bone structure in the patient.

Another feature of this invention is to provide an access channel at thedistal end of the retractor to allow passage of medical hardware.

Another feature of this invention is to provide retractors that are madefrom a series of predetermined sizes having tailored contouring that thesurgeon can select to match the depth of the cavity in the patient madeby the dilator.

The foregoing and other features of the present invention will becomemore apparent from the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the spine of a patient with thecannula shown in cross section inserted adjacent to the posteriorportion of the vertebra and having superimposed the cannula resting onthe bone of a prior art configuration;

FIG. 2 is an exploded view in perspective of the non cannulated dilator,a series of graduated increased diameter dilators and the cannula ordilator retractor of this invention;

FIG. 3 is a view in perspective illustrating the non cannulated dilator,the graduated dilators and the dilator retractor stacked over each otheras they would appear in the patient and the dilator retractor shown inphantom when the other elements are removed;

FIG. 4 is a schematic illustrating an embodiment of this invention wherethe dilator retractor is configured with the distal end being slanted toaccommodate the bone structure of the patient;

FIG. 5 is a schematic illustration exemplifying another embodiment ofthis invention where the dilator retractor is configured with a tunnelat the distal end;

FIG. 5A is a schematic illustration of the embodiment of FIG. 5 shown inproximity to a pedicle screw implanted in a vertebra;

FIG. 6 is a schematic illustration exemplifying another embodiment ofthis invention where the dilator retractor is configured in a funnelshape;

FIG. 7 is a photocopy of a drawing of the posterior view of the 3^(rd)and 4^(th) lumbar vertebrae with a schematic comparison of a circular incross section configured prior art dilator retractor and the dilatorretractor of this invention;

FIG. 8 is a schematic illustration of a series of different sizeddilator retractors sized to accommodate different lengths to fit theanatomical dimensions of patients; and

FIG. 9 exemplifies another series of varying length dilator retractorsas would available to the surgeon.

These figures merely serve to further clarify and illustrate the presentinvention and are not intended to limit the scope thereof.

DETAILED DESCRIPTION OF THE INVENTION

While the preferred embodiment of this invention is described herein, itwill be appreciated, as one skilled in this art will recognize, that theinvention although directed toward non-cylindrically shaped dilatorretractors, under certain circumstances, the invention contemplatescylindrically shaped dilator retractors where the bottom or distal endis configured to accommodate the shape of the bone structure of thepatient or to accommodate different procedures that are available to thesurgeon. As for example, the distal end of a cylindrically shapeddilator retractor may be tunneled so as to allow the insertion of animplant. The terms “cannula” and “dilator retractor” have the samemeaning and are used herein interchangeably. The term cavity as usedherein means the cavity that is created by the dilators and when thedilator retractor is inserted in this cavity it becomes a workingchannel for the surgeons use in performing the minimal invasive surgery.While the invention is particularly efficacious for use in performingminimal invasive surgery, as would be obvious to any skilled artisan,this invention would also be useful for other types of surgery.

While in the preferred embodiment the description of this inventiondetails the use of a non cannulated dilator of the type described andclaimed in the Cross Reference of this patent application and which isincorporated herein by reference, as one skilled in the art willappreciate, this invention also contemplates the use of a guide wire forcertain surgical procedures.

To better understand this invention reference is made to the prior artconfiguration of a dilator retractor as viewed in the target area of apatient. In this example, the patient is inflicted with a herniated discin the spinal column and the surgeon targets the posterior portion ofthe vertebra to perform the surgical procedure. The dilator retractor orcannula 10 is inserted in the body and up to where the distal end restson the bone structure. Obviously, there is a space from left to rightbetween the bone and the end of the dilator retractor and as mentionedabove, tufts of muscle remains in or migrates to this area. The surgeonneeds to remove this material before performing the procedure forrepairing the herniated disc to the discomfort of the patient.

In accordance with one embodiment of this invention and as best seen inFIGS. 2 and 3, a series of dilators 12, including the non-cannuladilator 14 serve to enlarge the cavity of the patient by inserting thefirst dilator or non-cannula dilator 14 into a incision in the skin ofthe patient and “working” the non-cannula dilator 14, a tool (not shown)engaging the proximal end by forcing and rocking it through the fibrousand muscle material until it reaches its target. The non-cannula dilatoris an elongated cylindrical solid body 16 having a tool engaging portion18 at the proximate end and a pointed tip portion 20 at the distal end.The tip 22 of the pointed tip portion is blunted and slightly rounded sothat it is unlike the tip of a common sewing needle, i.e. not razorsharp. The other dilators 12, being progressively shorter in length areall similarly constructed. Namely, they all are hollow so that eachprogressively shorter dilator passes over the previously inserteddilator and have a tool engaging end portion 24 at the proximate end anda beveled end portion 26 at the distal end that fares into a sharp edgeat the bottom thereof. The dilators function is well known and for thesake of convenience and brevity need not be detailed herein. Theinventive aspect of the dilators 12 is that they are configured in anelliptical or ovoid shape in cross section and the circumferentialdimension between the tool engaging portion 24 and the beveled endportion 26. The hollow portion of each of the dilators 18 are configuredto complement the outer surface of the preceding dilator and in theinstance of the non cannula dilator 14, the hollow portion of the nextsucceeding dilator 12 is circular in cross section rather than beingelliptical in cross section as are the next succeeding dilators 12.After the dilators 12 have been inserted into the patient, the dilatorretractor 30 is inserted over the last inserted dilator 12 and forcedinto position, typically with a template or anvil that fits over theproximate end 32 of the dilator retractor 30. The opposite end portion,similar to the dilators 12 is beveled and fares into a sharp edge 34.The hollow portion or straight through bore 26 is contoured identicallyto the contour of the preceding dilator 12. FIG. 3 demonstrates thepositions of the dilators 12 and the non cannula dilator 14 when finallyinserted into the patient. As seen in FIG. 3, the dilators 12 and noncannula dilator 14 are removed leaving the dilator retractor 30 inposition. Obviously, the dilator retractor 30 affords a wide channel forthe surgeon to pass his instruments therethrough allowing the surgeon toperform the surgical procedure while providing sufficient opening topermit the use of a microscope and lighting to view the area of thetarget.

As mentioned in the Background section of this patent application, inaccordance with this invention the distal ends of the dilator retractorsare “tailored” to meet certain criteria resulting from the anatomicalstructure of the target area of the patient. FIGS. 4, 5, and 6 exemplifyexamples of what is meant by the term “tailoring” and while thesedilator retractors represent the preferred embodiment, it will beunderstood by those skilled in this art that these are merely examplesand do not limit the scope of this invention. In FIG. 4, for example,the distal end 40 of dilator retractor 42 is sloped to follow to somedegree the slope of the posterior portion of the vertebra. The directionof the slope and the degree of the slope will be predicated onstatistical dimensions of these bone structure for a variety ofdifferent sized individuals. The cross sectional configuration of thedilator retractor 42 can take any of a number of different shapes, suchas elliptical, circular, etc.

FIG. 5 is similar in concept to FIG. 4 except that the dilator retractor44 includes a cut-out portion 46 at the distal end 48 and side 50 islonger than side 52 or like the dilator retractor 42 depicted in FIG. 4,the bottom portion can be sloped. Since the cut-out portion 46 is madethrough the side walls and bore of the dilator and dilator retractor, itis essentially a cut out of the side walls at diametrical locations atthe distal end and hence, defines a lateral passageway or tunnel toallow passage of an implant 45.

The dilator retractor 54 of FIG. 6 is similar to the dilator retractordepicted in FIG. 4 except that the configuration is funnel shaped.Namely, the upper portion 56 is conically shaped with the wider portionat the proximal end and fares into the cylindrical portion 58. Thedistal end 60 is sloped similar to the slope in the dilator retractor 42depicted in FIG. 4. Obviously, the wider proximal end affords a widerchannel that is available for use by the surgeon.

It is apparent from the foregoing and particularly with the embodimentsdepicted in FIGS. 4 and 5, the configuration of the dilator retractorscan take many shapes, namely cylindrical, elliptical or even polygonshape. Of course, in the preferred embodiment, the thickness of the wallover the major portion of the dilator retractors are uniform.

FIG. 7 is included to illustrate the comparison of the heretofore knowndilator retractors or cannulas and the dilator retractors or cannulasmade in accordance with certain embodiments of this invention. FIG. 7 isa photocopy of a drawing of the lumbar vertebrae showing the posteriorview. If the surgeon requires an access provided by the dilatorretractor to be say, 35 mm, which is approximately 16 mm larger than thecurrent available dilator retractors, the cylindrically shaped dilatorretractor would have to be sized with a 35 mm diameter, as depicted bythe circle X. Obviously, this sized dilator retractor would not fit intothe contour of the vertebral body (spinous process) as it would be toowide in the horizontal direction, although sufficiently wide in thevertical direction. In accordance with this invention the major accessof the elliptically shaped dilator retractor illustrated by the oval Zis in this example 35 mm and meets the requirement of the surgeon andthe minor axis or narrower portion fits into the channel defined by thebone structure of this portion of the spine. In other words, the dilatorretractor is contoured to the anatomical configuration of the patient orin other words is “tailored”. It being noted that the 16 mm cylindricaldilator retractor, although narrow enough in the horizontal direction,is not sufficient in the vertical direction.

FIGS. 8 and 9 exemplify embodiments of this invention where theparticular “tailored” shape of the dilator retractor is provided in kitsof different lengths to match the depth of the cavity of the workingarea of the patient. The kit may contain any number of sizes oralternatively, a facility, like a hospital, may inventory a given numberof sizes and shapes of the dilator retractor. In the embodiment depictedin FIG. 8 a series of different length dilator retractors or cannulas 70with the tunnel shaped distal end portion 72 are disclosed as apreferred embodiment and in FIG. 9 a series of different length ovoiddilator retractors 74 are depicted.

What has been shown by this invention is a novel, unique and functionaldilator retractor that is “tailored” to meet the anatomicalconfiguration of the patient. In addition, each of the configureddilator retractors are sized so that they conform to the depth of thecavity in which they are inserted into the patient. In addition to thebenefits of these configured dilator retractors that have beenenumerated above, these dilator retractors and the dilators associatedtherewith, afford opportunities to the surgeon to operate in areas ofthe spine that were not operable with minimal invasive surgeryheretofore or at best were operable with a given risk.

Although this invention has been shown and described with respect todetailed embodiments thereof, it will be appreciated and understood bythose skilled in the art that various changes in form and detail thereofmay be made without departing from the spirit and scope of the claimedinvention.

The invention claimed is:
 1. A method of positioning an implant relativeto a vertebra comprising: making a skin incision; inserting a cannulathrough the skin incision such that a lumen of the cannula defines aworking channel from the skin incision to a pedicle of the vertebra, thecannula having a cut-out formed in a sidewall of the cannula at a distalend of the cannula; introducing an implant into a proximal end of thecannula; and passing the implant through the cut-out in the sidewall ofthe cannula.
 2. The method of claim 1, wherein the implant comprises aspinal rod.
 3. The method of claim 1, wherein the distal end of thecannula includes a second cut-out formed in the sidewall of the cannula,the second cut-out diametrically opposed to the cut-out, the cut-outsproviding diametrically opposed lateral passages through the sidewall ofthe cannula at the distal end of the cannula.
 4. A method positioning animplant relative to a bone anchor, the method comprising: advancing animplant through a proximal end of a cannula, the cannula defining aworking channel extending from a skin incision to a bone anchorimplanted in a pedicle of a vertebra; and passing the implant through acut-out from in a sidewall of the cannula at a distal end of the cannulato position the implant relative to the bone anchor.
 5. The method ofclaim 4, wherein the implant is a rod.
 6. The method of claim 5, whereinthe bone anchor is a pedicle screw.
 7. A method of positioning animplant relative to a vertebra, comprising: inserting an instrumentthrough a pathway extending from a skin incision to a pedicle of avertebra, the instrument defining a working channel from the skinincision to proximate the vertebra; introducing an implant into aproximal end of the instrument; and passing the implant through acut-out formed in a sidewall of the instrument at a distal end of theinstrument to position the implant relative to the vertebra.
 8. Themethod of claim 7, wherein the implant comprises a spinal rod.
 9. Themethod of claim 7, wherein the instrument is a cannula.
 10. The methodof claim 7, wherein the distal end of the instrument includes a secondcut-out formed in the sidewall of the instrument, the second cut-outdiametrically opposed to the cut-out, the cut-outs providingdiametrically opposed lateral passages through the sidewall of theinstrument at the distal end of the instrument.